It is desirable to fill cavities, such as vias, trenches, and line patterns in an otherwise flat microelectronic substrate or integrated circuits. However, in coating the surface of the substrate with a metal film by such processes as evaporation, ion beam deposition, or sputtering, one serious problem arises. Self-shadowing of the deposited material results in a cavity being enclosed inside the cavity to be filled. This enclosed cavity will trap process chemicals and cause a serious reliability problem. This problem is especially serious for a cavity with a high aspect ratio that is common among today's microelectronics.
The present invention is directed to a process for depositing metal into and substantially filling the cavities on the flat surface of a substrate without leaving any film deposited on the flat surface. The present process is applicable to fill vias, and line patterns in substrate or integrated circuit processing. For example, the process can be used to build a coaxial conductor into a substrate by providing a line pattern in a cavity etched into a dielectric layer and alternating layers of conductor and dielectric can be deposited to build a coaxial conductor.